--- name: "__gnu_parallel::_Settings" section: "3" platform: "linux" package: "gcc" version: "16.2.1+r23+gd564253eb6c8-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/__gnu_parallel::_Settings" --- # \_\_gnu\_parallel::\_Settings(3) class \_Settings Run-time settings for the parallel mode including all tunable parameters. ## NAME \_\_gnu\_parallel::\_Settings - class \_Settings Run-time settings for the parallel mode including all tunable parameters. ## SYNOPSIS \#include \ ### Static Public Member Functions static const \_Settings & **get** () throw ()\ Get the global settings. static void **set** (\_Settings &) throw ()\ Set the global settings. ### Public Attributes **\_SequenceIndex** **accumulate\_minimal\_n**\ Minimal input size for accumulate. unsigned int **adjacent\_difference\_minimal\_n**\ Minimal input size for adjacent\_difference. **\_AlgorithmStrategy** **algorithm\_strategy**\ unsigned int **cache\_line\_size**\ Overestimation of cache line size. Used to avoid false sharing, i.e. elements of different threads are at least this amount apart. **\_SequenceIndex** **count\_minimal\_n**\ Minimal input size for count and count\_if. **\_SequenceIndex** **fill\_minimal\_n**\ Minimal input size for fill. **\_FindAlgorithm** **find\_algorithm**\ double **find\_increasing\_factor**\ Block size increase factor for find. **\_SequenceIndex** **find\_initial\_block\_size**\ Initial block size for find. **\_SequenceIndex** **find\_maximum\_block\_size**\ Maximal block size for find. float **find\_scale\_factor**\ Block size scale-down factor with respect to current position. **\_SequenceIndex** **find\_sequential\_search\_size**\ Start with looking for this many elements sequentially, for find. **\_SequenceIndex** **for\_each\_minimal\_n**\ Minimal input size for for\_each. **\_SequenceIndex** **generate\_minimal\_n**\ Minimal input size for generate. unsigned long long **L1\_cache\_size**\ size of the L1 cache in bytes (underestimation). unsigned long long **L2\_cache\_size**\ size of the L2 cache in bytes (underestimation). **\_SequenceIndex** **max\_element\_minimal\_n**\ Minimal input size for max\_element. **\_SequenceIndex** **merge\_minimal\_n**\ Minimal input size for merge. unsigned int **merge\_oversampling**\ Oversampling factor for merge. **\_SplittingAlgorithm** **merge\_splitting**\ **\_SequenceIndex** **min\_element\_minimal\_n**\ Minimal input size for min\_element. **\_MultiwayMergeAlgorithm** **multiway\_merge\_algorithm**\ int **multiway\_merge\_minimal\_k**\ Oversampling factor for multiway\_merge. **\_SequenceIndex** **multiway\_merge\_minimal\_n**\ Minimal input size for multiway\_merge. unsigned int **multiway\_merge\_oversampling**\ Oversampling factor for multiway\_merge. **\_SplittingAlgorithm** **multiway\_merge\_splitting**\ **\_SequenceIndex** **nth\_element\_minimal\_n**\ Minimal input size for nth\_element. **\_SequenceIndex** **partial\_sort\_minimal\_n**\ Minimal input size for partial\_sort. **\_PartialSumAlgorithm** **partial\_sum\_algorithm**\ float **partial\_sum\_dilation**\ Ratio for partial\_sum. Assume *sum*and*write*result"*to*be*this*factor*slower*than*just*sum*.* unsigned int **partial\_sum\_minimal\_n**\ Minimal input size for partial\_sum. double **partition\_chunk\_share**\ Chunk size for partition, relative to input size. If \> 0.0, this value overrides partition\_chunk\_size. **\_SequenceIndex** **partition\_chunk\_size**\ Chunk size for partition. **\_SequenceIndex** **partition\_minimal\_n**\ Minimal input size for partition. **\_SequenceIndex** **qsb\_steals**\ The number of stolen ranges in load-balanced quicksort. unsigned int **random\_shuffle\_minimal\_n**\ Minimal input size for random\_shuffle. **\_SequenceIndex** **replace\_minimal\_n**\ Minimal input size for replace and replace\_if. **\_SequenceIndex** **search\_minimal\_n**\ Minimal input size for search and search\_n. **\_SequenceIndex** **set\_difference\_minimal\_n**\ Minimal input size for set\_difference. **\_SequenceIndex** **set\_intersection\_minimal\_n**\ Minimal input size for set\_intersection. **\_SequenceIndex** **set\_symmetric\_difference\_minimal\_n**\ Minimal input size for set\_symmetric\_difference. **\_SequenceIndex** **set\_union\_minimal\_n**\ Minimal input size for set\_union. **\_SortAlgorithm** **sort\_algorithm**\ **\_SequenceIndex** **sort\_minimal\_n**\ Minimal input size for parallel sorting. unsigned int **sort\_mwms\_oversampling**\ Oversampling factor for parallel std::sort (MWMS). unsigned int **sort\_qs\_num\_samples\_preset**\ Such many samples to take to find a good pivot (quicksort). **\_SequenceIndex** **sort\_qsb\_base\_case\_maximal\_n**\ Maximal subsequence \_\_length to switch to unbalanced \_\_base case. Applies to std::sort with dynamically load-balanced quicksort. **\_SplittingAlgorithm** **sort\_splitting**\ unsigned int **TLB\_size**\ size of the Translation Lookaside Buffer (underestimation). **\_SequenceIndex** **transform\_minimal\_n**\ Minimal input size for parallel std::transform. **\_SequenceIndex** **unique\_copy\_minimal\_n**\ Minimal input size for unique\_copy. **\_SequenceIndex** **workstealing\_chunk\_size**\ ## Detailed Description class \_Settings Run-time settings for the parallel mode including all tunable parameters. ## Member Function Documentation ### const \_Settings & \_\_gnu\_parallel::\_Settings::get () \[static\] Get the global settings. Referenced by **\_\_gnu\_parallel::\_\_find\_template()**, **\_\_gnu\_parallel::\_\_find\_template()**, **\_\_gnu\_parallel::\_\_find\_template()**, **\_\_gnu\_parallel::\_\_for\_each\_template\_random\_access\_workstealing()**, **\_\_gnu\_parallel::\_\_parallel\_nth\_element()**, **\_\_gnu\_parallel::\_\_parallel\_partial\_sum()**, **\_\_gnu\_parallel::\_\_parallel\_partial\_sum\_linear()**, **\_\_gnu\_parallel::\_\_parallel\_partition()**, **\_\_gnu\_parallel::\_\_parallel\_random\_shuffle\_drs()**, **\_\_gnu\_parallel::\_\_parallel\_sort()**, **\_\_gnu\_parallel::\_\_parallel\_sort()**, **\_\_gnu\_parallel::\_\_parallel\_sort\_qs\_conquer()**, **\_\_gnu\_parallel::\_\_qsb\_local\_sort\_with\_helping()**, **\_\_gnu\_parallel::\_\_sequential\_random\_shuffle()**, **\_\_gnu\_parallel::multiway\_merge\_sampling\_splitting()**, **\_\_gnu\_parallel::parallel\_multiway\_merge()**, **\_\_gnu\_parallel::parallel\_sort\_mwms()**, and **\_\_gnu\_parallel::parallel\_sort\_mwms\_pu()**. ### void \_\_gnu\_parallel::\_Settings::set (\_Settings & ) \[static\] Set the global settings. References **accumulate\_minimal\_n**, **adjacent\_difference\_minimal\_n**, **cache\_line\_size**, **count\_minimal\_n**, **fill\_minimal\_n**, **find\_increasing\_factor**, **find\_initial\_block\_size**, **find\_maximum\_block\_size**, **find\_scale\_factor**, **find\_sequential\_search\_size**, **for\_each\_minimal\_n**, **generate\_minimal\_n**, **L1\_cache\_size**, **L2\_cache\_size**, **max\_element\_minimal\_n**, **merge\_minimal\_n**, **merge\_oversampling**, **min\_element\_minimal\_n**, **multiway\_merge\_minimal\_k**, **multiway\_merge\_minimal\_n**, **multiway\_merge\_oversampling**, **nth\_element\_minimal\_n**, **partial\_sort\_minimal\_n**, **partial\_sum\_dilation**, **partial\_sum\_minimal\_n**, **partition\_chunk\_share**, **partition\_chunk\_size**, **partition\_minimal\_n**, **qsb\_steals**, **random\_shuffle\_minimal\_n**, **replace\_minimal\_n**, **search\_minimal\_n**, **set()**, **set\_difference\_minimal\_n**, **set\_intersection\_minimal\_n**, **set\_symmetric\_difference\_minimal\_n**, **set\_union\_minimal\_n**, **sort\_minimal\_n**, **sort\_mwms\_oversampling**, **sort\_qs\_num\_samples\_preset**, **sort\_qsb\_base\_case\_maximal\_n**, **TLB\_size**, **transform\_minimal\_n**, and **unique\_copy\_minimal\_n**. Referenced by **set()**. ## Member Data Documentation ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::accumulate\_minimal\_n Minimal input size for accumulate. Referenced by **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::adjacent\_difference\_minimal\_n Minimal input size for adjacent\_difference. Referenced by **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::cache\_line\_size Overestimation of cache line size. Used to avoid false sharing, i.e. elements of different threads are at least this amount apart. Referenced by **\_\_gnu\_parallel::\_\_for\_each\_template\_random\_access\_workstealing()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::count\_minimal\_n Minimal input size for count and count\_if. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::fill\_minimal\_n Minimal input size for fill. Referenced by **set()**. ### double \_\_gnu\_parallel::\_Settings::find\_increasing\_factor Block size increase factor for find. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::find\_initial\_block\_size Initial block size for find. Referenced by **\_\_gnu\_parallel::\_\_find\_template()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::find\_maximum\_block\_size Maximal block size for find. Referenced by **set()**. ### float \_\_gnu\_parallel::\_Settings::find\_scale\_factor Block size scale-down factor with respect to current position. Referenced by **\_\_gnu\_parallel::\_\_find\_template()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::find\_sequential\_search\_size Start with looking for this many elements sequentially, for find. Referenced by **\_\_gnu\_parallel::\_\_find\_template()**, **\_\_gnu\_parallel::\_\_find\_template()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::for\_each\_minimal\_n Minimal input size for for\_each. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::generate\_minimal\_n Minimal input size for generate. Referenced by **set()**. ### unsigned long long \_\_gnu\_parallel::\_Settings::L1\_cache\_size size of the L1 cache in bytes (underestimation). Referenced by **set()**. ### unsigned long long \_\_gnu\_parallel::\_Settings::L2\_cache\_size size of the L2 cache in bytes (underestimation). Referenced by **\_\_gnu\_parallel::\_\_parallel\_random\_shuffle\_drs()**, **\_\_gnu\_parallel::\_\_sequential\_random\_shuffle()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::max\_element\_minimal\_n Minimal input size for max\_element. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::merge\_minimal\_n Minimal input size for merge. Referenced by **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::merge\_oversampling Oversampling factor for merge. Referenced by **\_\_gnu\_parallel::multiway\_merge\_sampling\_splitting()**, **\_\_gnu\_parallel::parallel\_multiway\_merge()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::min\_element\_minimal\_n Minimal input size for min\_element. Referenced by **set()**. ### int \_\_gnu\_parallel::\_Settings::multiway\_merge\_minimal\_k Oversampling factor for multiway\_merge. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::multiway\_merge\_minimal\_n Minimal input size for multiway\_merge. Referenced by **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::multiway\_merge\_oversampling Oversampling factor for multiway\_merge. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::nth\_element\_minimal\_n Minimal input size for nth\_element. Referenced by **\_\_gnu\_parallel::\_\_parallel\_nth\_element()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::partial\_sort\_minimal\_n Minimal input size for partial\_sort. Referenced by **set()**. ### float \_\_gnu\_parallel::\_Settings::partial\_sum\_dilation Ratio for partial\_sum. Assume "sum and write result" to be this factor slower than just "sum". Referenced by **\_\_gnu\_parallel::\_\_parallel\_partial\_sum\_linear()**, and **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::partial\_sum\_minimal\_n Minimal input size for partial\_sum. Referenced by **set()**. ### double \_\_gnu\_parallel::\_Settings::partition\_chunk\_share Chunk size for partition, relative to input size. If \> 0.0, this value overrides partition\_chunk\_size. Referenced by **\_\_gnu\_parallel::\_\_parallel\_partition()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::partition\_chunk\_size Chunk size for partition. Referenced by **\_\_gnu\_parallel::\_\_parallel\_partition()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::partition\_minimal\_n Minimal input size for partition. Referenced by **\_\_gnu\_parallel::\_\_parallel\_nth\_element()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::qsb\_steals The number of stolen ranges in load-balanced quicksort. Referenced by **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::random\_shuffle\_minimal\_n Minimal input size for random\_shuffle. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::replace\_minimal\_n Minimal input size for replace and replace\_if. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::search\_minimal\_n Minimal input size for search and search\_n. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::set\_difference\_minimal\_n Minimal input size for set\_difference. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::set\_intersection\_minimal\_n Minimal input size for set\_intersection. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::set\_symmetric\_difference\_minimal\_n Minimal input size for set\_symmetric\_difference. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::set\_union\_minimal\_n Minimal input size for set\_union. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::sort\_minimal\_n Minimal input size for parallel sorting. Referenced by **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::sort\_mwms\_oversampling Oversampling factor for parallel std::sort (MWMS). Referenced by **\_\_gnu\_parallel::parallel\_sort\_mwms()**, **\_\_gnu\_parallel::parallel\_sort\_mwms\_pu()**, and **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::sort\_qs\_num\_samples\_preset Such many samples to take to find a good pivot (quicksort). Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::sort\_qsb\_base\_case\_maximal\_n Maximal subsequence \_\_length to switch to unbalanced \_\_base case. Applies to std::sort with dynamically load-balanced quicksort. Referenced by **\_\_gnu\_parallel::\_\_qsb\_local\_sort\_with\_helping()**, and **set()**. ### unsigned int \_\_gnu\_parallel::\_Settings::TLB\_size size of the Translation Lookaside Buffer (underestimation). Referenced by **\_\_gnu\_parallel::\_\_parallel\_random\_shuffle\_drs()**, **\_\_gnu\_parallel::\_\_sequential\_random\_shuffle()**, and **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::transform\_minimal\_n Minimal input size for parallel std::transform. Referenced by **set()**. ### \_SequenceIndex \_\_gnu\_parallel::\_Settings::unique\_copy\_minimal\_n Minimal input size for unique\_copy. Referenced by **set()**. ## Author Generated automatically by Doxygen for libstdc++ from the source code.